1. Field of the Invention
This invention pertains to a novel photometer apparatus and system especially adapted for use in an aircraft. More particularly, it relates to such an apparatus and system which does not have to be pointed through a window in the aircraft. Most especially, it relates to such an apparatus and system which will allow observations of the sun to be made during a substantially greater portion of the aircraft flight than with the prior art apparatus and systems.
2. Description of the Prior Art
A variety of apparatus and systems for tracking solar and other light sources are known in the art. For example, such apparatus and systems are disclosed in the following issued U.S. Pat. Nos.: 2,972,812, issued Feb. 28, 1961 to Jackson, Jr.; 2,975,289, issued Mar. 14, 1961 to Robert et al.; 4,173,414, issued Nov. 6, 1979 to Vauchy et al.; 4,329,579, issued May 11, 1982 to Jansen et al.; 4,332,238, issued June 1, 1982 to Garcia, Jr.; 4,367,403, issued Jan. 4, 1983 to Miller; 4,440,150, issued Apr. 3, 1984 to Kaehler and 4,445,030, issued Apr. 24, 1984 to Carlton. However, none of the apparatus and systems disclosed in these patents is particularly adapted for use in an aircraft.
A variety of sensors for determining the position of the sun or other light sources are also known in the art. For example, such sensors are disclosed in the following issued U.S. Pat. Nos.: 3,670,168, issued June 13, 1972 to Low et al.; 3,951,550, issued April 20, 1976 to Slick; 4,181,435 issued Jan. 1, 1980 to Williamson et al.; 4,315,690, issued Feb. 16, 1982 to Trocellier et al.; 4,424,801, issued Jan. 10, 1984 to Mori and 4,484,565, issued Nov. 27, 1984 to Mori. However, none of these sensors are incorporated into an apparatus or system particularly adapted for use in an aircraft.
While the art relating to such apparatus, systems and sensors is a well developed one, the approach that has hitherto been employed is to use apparatus and systems for tracking and sensors for determining light source position that are not especially designed for aircraft use by pointing the apparatus, systems and sensors through a cabin window of the aircraft. When used for solar measurements, this approach requires that the aircraft be maneuvered to keep the apparatus pointed at the sun through the window. Such apparatus and systems also require that the window be removed from the aircraft before and after each flight for calibration purposes. Obviously, such removal is both troublesome and undesirable with respect to the structural integrity of the aircraft.